By Richard V. Miller, Princeton University, USA
Inflammation helps us in the short term by combating infections and other stresses. But over the long term, we do not want too much inflammation. Chronic inflammation plays a role in disorders like arthritis, lupus, and even cancer. Modern medicine has spawned some great anti-inflammatory medications that offer relief from chronic inflammation, including the nonsteroidal anti-inflammatory drugs and steroids. Perhaps unsurprisingly, research shows that nature makes its own anti-inflammatory compounds, and sometimes they can be found in the foods that we eat.
It turns out that our diets can have significant effects on our bodies’ inflammatory responses. In fact, people in nutritional studies who report diets lower in saturated fats tend to produce lower levels of pro-inflammatory biomarkers like interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α). Pro-inflammatory biomarkers then act as signals for the body to turn on the inflammatory response, which includes changes in the immune system. So foods that increase the ratio of unsaturated to saturated fats tend to have a negative effect on inflammatory biomarkers.
There is evidence that the following foods can reduce inflammatory biomarkers:
This group of fish—like tuna, salmon, sardines, anchovies, and mackerel—is a source of unsaturated fats called omega-3 fatty acids. An analysis of 26 studies showed that omega-3 intake was associated with lower levels of inflammatory biomarkers in human subjects. However, a more recent review analyzed a larger sample of randomized studies and concluded that some studies did not show a strong effect, so more research will be needed. There also appears to be a balance to be struck when it comes to omega-3 consumption. A 2013 review of studies in non-human animals argued that excess omega-3 consumption can lead to negative effects like harmful changes in the immune system.
You might have avoided them as a child, but vegetables really are part of a healthy diet. A 2014 study looked at the effect of diets rich in cruciferous vegetables—like broccoli, Brussels sprouts, kale, arugula, and others—on healthy young adults. The researchers concluded that the diet reduced levels of the inflammatory biomarker IL-6, but other tested biomarkers were either unaffected or even increased. A larger study focusing on female subjects showed that omega-3 intake was associated with lower levels of the inflammatory biomarkers IL-6, IL-1β and TNF-α.
The Mediterranean diet is often touted as a sensible way to eat, and proponents often point to olive oil as an important part of the diet. A 2015 meta-analysis of 30 randomized studies concluded that moderate olive oil consumption might reduce levels of the inflammatory biomarkers IL-6 and C-reactive protein. The helpful effect could come from olive oil’s high unsaturated fat content relative to saturated fat, but more research will be needed to support this claim.
Tree nuts and peanuts also have a favorable ratio of unsaturated to saturated fats. A 2016 study concluded that self-reported diets that were higher in tree nuts—like walnuts, almonds, and pecans—were associated with lower levels of inflammatory biomarkers. In addition, a 2014 review concluded that nuts can reduce the effects of the metabolic syndrome, which might partially explain their effect on inflammation.
The science seems to suggest that a diet that includes these foods is associated with lower levels of the signaling molecules that our bodies use to turn on inflammation. Even if they do not have any significant anti-inflammatory effects, all the foods mentioned can be parts of a healthy diet when eaten in moderation. More research will need to be done to understand the extent of their putative anti-inflammatory effects and to advise people who include them in their diets.
I am a biologist and science writer with an interest in genetics and how the public interacts with science. If I’m not doing my own experiments or writing about someone else’s, you can find me exploring New York City or watching baseball.
This post is the second in our inflammation series. The first post – Fibrosis: an overlooked companion of inflammation by Conor Sugden – was published earlier this month. If you are interested in reading more on this topic, you can also check out the August issue of The Biochemist magazine on the theme of inflammation.